In wireless communication network, information about the format in which the data is to be communicated between network nodes is transmitted as control information in a specified and known way. The receiving node, e.g. a User Equipment (UE) in a Long Term Evolution (LTE) network, first decodes the control information, also referred to as a grant, which control information contains information on the transport format of the transmitted downlink data and/or the data to be transmitted uplink. Examples of the formatting information are allocation, i.e. where the data is located, typically in frequency, number of layers used, modulation and coding information, and HARQ process index.
In LTE networks, the grant is transmitted on a Physical Downlink Control Channel (PDCCH) or an enhanced Physical Downlink Control Channel (ePDCCH) using a variety of Downlink Control Information (DCI) formats which are specific to different operating modes of the UE. For example, in the random access procedure the Enhanced NodeB (eNB), when sending a random access response to the UE, uses a DCI format 1A. The eNB uses this format since this is known to all UEs and the eNB does not know the actual capabilities of the UE when sending the random access response. Later in the call setup procedure the eNB learn the UE capabilities and can start using a more advanced DCI format.
A grant received on PDCCH/ePDCCH is relative a specific subframe (except semi-persistent grants that are relative multiple subframes). For downlink (DL) the grant is typically specific to same subframe n in which the grant was detected, while for uplink (UL) the grant is typically specific to a future subframe n+a. Usually a=4.
In some scenarios it would be desired to send the next grant inside a granted PDCH transmission. Such a nested scenario of grants will in the present disclosure be denoted as a “daisy chain”. However, the daisy chain scheme suffers from error propagation.
If UE fails to detect the first grant on PCCH the UE will also fails to detect sub-sequent transmissions on PDCH, and the UE will not send anything in UL either. Error propagation can be terminated due to that eNB detects that UE does not perform a granted UL transmission. Although that error propagation can be terminated after some time the performance loss can still be significant. Hence, a better method for mitigating error propagation is needed before a daisy-chain scheme can provide acceptable performance.